A method for monitoring the temperature of at least one bearing of an electrical machine, a monitoring device which corresponds to it, as well an electrical machine having a monitoring device such as this.
The present invention relates to a method for monitoring the temperature of at least one bearing of an electrical machine, such as a motor or a generator, which has a plurality of components such as a stator, a rotor and windings. The present invention also relates to a corresponding monitoring device, and to an electrical machine having a monitoring device such as this.
DE 103 05 368 A1 discloses methods and apparatuses in which relevant components of the electrical machine are monitored, effectively in real time, by an evaluation apparatus by means of temperature sensors which operate without making contact.
It is also known that the bearings of an electrical machine are subject to severe fatigue and/or to severe wear, in particular, when the electrical machine is excessively heavily loaded. This can lead to failure of the bearing and, in the end, of the electrical machine.
In addition, an excessively high temperature difference between the outer and inner part of the bearing, the so-called bearing outer ring and the so-called bearing inner ring, can result in the bearing becoming jammed, as a result of thermal stresses. Temperature differences such as these, in particular of a value of more than about 80° C., lead to severely accelerated wear and in consequence to rapid failure of the bearing or of the entire electrical machine. The reason for such high temperature differences is a high thermal power loss which is caused by remagnetization processes in the rotor and which can be dissipated from the rotor only with difficulty.
It is admittedly also possible, as described in DE 103 05 368 A1, for the temperature of rotating components, for example of the rotor, to be detected without contact being made. However, the extremely confined spatial conditions in a compact electrical machine do not allow reliable measured-value detection.